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Homework Help: Volume and Density

  1. Dec 8, 2008 #1
    1. The problem statement, all variables and given/known data

    A samoke of unknown material weighs 300N in air and 200N when immersed in alcohol of specific gravity 0.7. Find the volume and density of the material

    2. Relevant equations

    Specific Gravity = density of material/density of water

    Density fluid x volume of fluid x gravity = density material x volume of material x gravity

    3. The attempt at a solution

    Volume of substance = Density of Fluid x Volume of fluid / Density of material

    The density of the substance can be using the specific gravity equation.

    I am not sure how to solve for the volume and density though
  2. jcsd
  3. Dec 8, 2008 #2


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    In the alcohol it is pushed up by a force equal to the weight of alcohol displaced.
    Since you know the force difference, you can work out the volume of alcohol and so the volume of the thing.
  4. Dec 8, 2008 #3
    So is it

    Fb= V x density x gravity
    V = 100N/(700kg/m3 x 9.8)
  5. Dec 8, 2008 #4


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    The units balance - you can check the arithmetic by putting the answer back into the question and checking you get the same bouyant force
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